Switchboards for mounting and supplying electrical power to a plurality of circuit breakers are well known in the art. However, the total amperage which can be handled by a switchboard is limited due to heat radiated by the breakers. In this regard, attempts in the 1970's to develop a 3,000 ampere alternating current switchboard failed due to excessive heat within the circuit breakers. More specifically, the failure was in meeting the specified Underwriters Laboratories temperature limits on the circuit breaker load cables, or at the line side plug-on connectors. Moreover, heretofore access to the various lug assemblies of conventional switchboards has been restrictive, making cable connections and other wiring tasks difficult and time consuming.
U.S. Pat. No. 5,166,861 issued to the inventor of the present application discloses a switchboard which provides for cooler circuit breaker operation, such that a longer power stack can be used and more and larger circuit breakers can be mounted in a single switchboard. It discloses a switchboard that is inexpensive to manufacture and maintain that affords ready access to the neutral bus bar assembly, the ground bus lug mounting assembly, and the other components of the switchboard.
The switchboard of the '861 patent comprises a frame including a center mounting pan, and including at least first and second circuit breaker mounting pans for engaging and supporting the rear end portions of the circuit breakers. The first circuit breaker mounting pan is selectively spaced from the center mounting pan so as to define an open area therebetween, and the second circuit breaker mounting pan is oppositely disposed with respect to the first circuit breaker mounting pan relative to the center mounting pan and is selectively spaced from the center mounting pan so as to define an open area therebetween. The switchboard also comprises a power stack assembly mounted on the center mounting pan of the frame. The power stack assembly includes first, second and third, substantially vertical, elongated main bus bar members for being connected to a source of electrical power and for releasably engaging the circuit breakers. The first main bus bar member is selectively spaced from the center mounting pan with insulator members so as to define a first ventilation passageway therebetween. The second main bus bar member is selectively spaced from the first main bus bar member with insulator members so as to define a second ventilation passageway therebetween. Similarly, the third main bus bar member is selectively spaced from the second main bus bar member with insulator members so as to define a third ventilation passageway therebetween. The power stack assembly further including a channel vent cover selectively spaced from the third main bus bar member with insulating members so as to define a forth ventilation passageway therebetween. Each of the first, second and third ventilation passageways defines an opening at the lower end of the power stack assembly and an opening at the upper end of the power stack assembly. The fourth ventilation passageway defines an opening proximate the lower end of the channel vent cover and an opening proximate the upper end of the channel vent cover. Resultantly, convection air is allowed to rise within the ventilation passageways to cool the power stack assembly. In addition, the center mounting pan and the main bus bars are provided with ventilation openings along their lengths to further facilitate air flow through the power stack assembly.
As illustrated in FIGS. 1 and 2 the switchboard 10 of the '861 patent is provided with a front assembly, including, in the preferred embodiment, upper and lower vented covers 30 and 32, respectively, and top and bottom covers 34 and 36, respectively, which are engaged to and extend between the front portions of the vertical support channels 18 and 20. Also included are removable cover panels 38, 40 and 42, which provide access to various components of the switchboard 10. Further, as illustrated by the phantom lines 44 in FIG. 2, the switchboard 10 can also be provided with a suitable enclosure for housing the frame 16 and various components of the switchboard 10. It will be recognized that the enclosure 44 can be formed by securing wall panels to the frame 16.
Located behind the panel 40 of switchboard 10 is a power stack assembly 12 for releasably mounting the circuit breakers 14. As shown in FIG. 3 the multi-pan mounting assembly includes a center pan 46 which supports the power stack assembly 12. The center pan 46 is secured to the mounting channels 22 of the frame 16 such that the center pan 46 is vertically disposed. Further, the center pan 46 is provided with a plurality of selectively spaced holes (not shown) for receiving suitable fasteners for securing the power stack assembly 12, and a plurality of ventilation openings (not shown) for providing air circulation through the power stack assembly 12.
As best illustrated in FIG. 3, the power stack assembly 12 includes three vertically disposed main bus bars 52, 54 and 56 to accommodate a three phase power supply. The main bus bars 52, 54 and 56 are secured together in selectively spaced, substantially parallel alignment with insulating means being provided between the bus bars to electrically insulate the bus bars from one another. The resulting assembly 12 is secured, in selectively spaced, substantially parallel alignment, to the center pan 46, with suitable insulation means being provided between the inner bus bar 52 and the center pan 46.
As seen in FIG. 3, the main bus bar 56 is connected to a main bus connecting member 124 which consists of a pair of vertically separated connecting members for conveying power from a through bus connector at the rear of the circuit breaker (not shown) to the bus bar 56: the through bus connector is in turn connected to one of the phases of the power supply. The use of a pair of main bus connecting members is required to handle the power requirements while, at the same time, avoiding an excessive temperature rise. Other main bus connecting members, located behind the main bus connecting member 124, provide power connection to the main bus bars 52 and 54 for the other two phases. Further, a stack top channel vent cover 88 is provided to cover the outer bus bar 56, with two spaced rows of outer insulating members 90 being provided between the bus bar 56 and the cover 88. The bus bars 52, 54 and 56, and the cover 88, with insulating members therebetween, are secured together and mounted on the center pan 46 with suitable fasteners (not shown in FIG. 3).
The main bus connecting members in the '861 invention are connected to corresponding lug pad connectors secured to a bus support channel carrying three lug pads: the lug pads, in turn, facilitate the connection of electrical cables from the electrical supply source.
As seen in FIGS. 1-3, circuit breakers are arranged on both sides of the power stack assembly 12. Due to the location of thee main bus connecting members on the right side of the switchboard when viewed from the front, there is less space available for mounting circuit breakers on the rights side of the power stack assembly 12. The circuit breakers 14 are provided with electrical connecting jaws (not shown) which releasably engage the outer edges (not shown) of the bus bars 52, 54 and 56. Suitable provision is made for supporting the circuit breakers by means of additional mounting pans.
It would be desirable to have a switchboard with increased height so as to be able to include additional circuit breakers in the switchboard. Such a switchboard should have improved heat dissipation capacity and have complete flexibility in the position of the circuit breakers. Such a switchboard should preferably use less material without a significant reduction in the electrical capacity. It would also be desirable to have a switchboard that provides increased flexibility to the user on the height at which power is input to the assembly. The present invention satisfies these requirement.